Right. The practical reality of business to day is that if you "do business" with someone, you're going to be signing some kind of agreement - a purchase agreement, or a longer more detailed contractual agreement.
So you are saying that Moslem businessmen can bind non-Moslems to Sharia just by waving a lot of money at them, and getting them to sign an agreement with Sharia in the boilerplate. "It's our standard contract ..... you submit or die."